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Topic: Herky-Jerky (Read 1773 times) previous topic - next topic

Herky-Jerky

88 Cougar w/ Rebuilt mustang block, 19#, 9AL, typhoon intake, Windsor JR. Heads w/ 1.6 roller rockers, hardened push rods, guide plates, and a TrickFlow Stage 1 cam.  2.5" exhaust w/o cats.  All backed up by a WC T-5 out of a 90 GT.

The engine has bout 4 miles on it.  It drives pretty good but when decelerating with the clutch out (transmission engaged) its herky-jerky.  I also noticed a little bit of popping in the intake when I was timing it.  Its running premium with about 11-12* of timing.

It has a MAF that could be the wrong part number.  It starts and idles fine and has great power.

I read on The Corral that this could be a lean condition and that the quick fix is to get a adjustable FPR and crank up the psi until it stops popping/bucking.  Permanent fix being a tune.

Any thoughts?

Herky-Jerky

Reply #1 –
Does it throw any codes?
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Herky-Jerky

Reply #2 –
I shall try pulling them tonight, although I suspect its just a bunch of complaints about the EGR.

Herky-Jerky

Reply #3 –
What do you mean "could be" the wrong MAF?

You shouldn't have the aircleaner in the engine bay.

Adjustable FPR won't stop the engine from learning around the change in fuel pressure.
11.96 @ 118 MPH old 306 KB; 428W coming soon.

Herky-Jerky

Reply #4 –
Quote from: Cougar5.0;290422
What do you mean "could be" the wrong MAF?
"Could be" as in it starts, runs, and drives great with the exception of the coast-down bucking.  The PN matches what some people claim to be compatible although not all lists Iv'e seen contain it.

Quote from: Cougar5.0;290422
You shouldn't have the aircleaner in the engine bay.
Yes I know.  I will install a 90* elbow when the car is road ready.  This is just for testing.  I'll loose a couple ponys until I install the 90.

Quote from: Cougar5.0;290422
Adjustable FPR won't stop the engine from learning around the change in fuel pressure.
I have issues at or near idle.  I don't have a WB to see where else it may be leaning out at (if its leaning out at all).

I guess my question should be "Would leaning out near idle cause the engine to buck?" I intend to pull codes as I am beginning to suspect its a TPS.

Also. My IAC is nice and clean.

Herky-Jerky

Reply #5 –
What size is the MAF?

Aircleaner in the engine bay does more than lose HP, the fan wash interferes with the MAF signal. Also, stock MAF wasn't designed to work with a cone filter. Adding an elbow in front of the MAF can cause problems too since it forces the air against one side of the MAF.
11.96 @ 118 MPH old 306 KB; 428W coming soon.

Herky-Jerky

Reply #6 –
Well.  Its a 70mm.  It is what it is.  I don't have a stock airbox that accepts the MAF and I had the cone filter and adapter sitting around.

Herky-Jerky

Reply #7 –
If it's a 70mm '93 Cobra style Ford meter it won't work too well - I tried the same before I got a tuner.
11.96 @ 118 MPH old 306 KB; 428W coming soon.

Herky-Jerky

Reply #8 –
It was the MAF.  I had a 70mm and a 65mm and they both were very herky jerky.  I went to the junkyard today and got a F1ZF12B579A from an 91 Merc Cougar 3.8L and it runs pretty good.  :burnout:

It's only a 55mm.  Any hope of swapping into a larger housing? I am assuming no.

With a little bit of learning the car runs great now.  I think I will put a few more degrees of timing into it.  I feel theres more HP lurking under there somewhere.  I just need to get a filter setup for it.

Herky-Jerky

Reply #9 –
Get 24lb injectors and the maf to match.
19lber's are barely enough for a stock HO let alone an HO with heads/cam/intake combo.
If you run premium(which you should be anyways)you can run between 13-14 degrees timing which should be optimal.
On a side note,did you change out your fuel pump for at least a 155lph???

Herky-Jerky

Reply #10 –
If you want to run a 70mm MAF you need one from on of the following cars:

94-95 Mustang (3.8 or 5.0)
92-94 Crown Vic, Grand Marquis, or Town Car 4.6

The sensor part number will start with F2VF. If it does you're good and you can use it with your A9L/P MAF computer. It works fine as I've been running one for over a year with no codes or other problems.

Just a FYI but you'll have to cut the  off to make it work. It's not hard to do. The other option is to use the 70mm housing from a 94-95 3.8 or 4.6 T-bird/Cougar. Just make sure you swap the F2VF sensor into the T-bird/Cougar 70mm housing as the sensor in the T-bird/Cougar housing will NOT work with your computer. I've run the F2VF sensor in the stock Crown Vic housing as well as swapping it into a 95 T-bird housing and it's run fine both ways.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Herky-Jerky

Reply #11 –
I will check the PN tonight but I am pretty sure thats what I grabbed from the JY the first round that gave me all the issues.
-z

Herky-Jerky

Reply #12 –
Thunderjet,

I checked the PN on my 70mm MAF and it is a F2VF part number.  Got it from an 92 crown vic.  When I timed the engine with it, it would pop through the intake and ping under load, and give a horrible case of herky-jerky while engine braking.  Is my fuel pump to blame? Do you run an adjustable regulator?  Maybe I will try sticking it on there again and running my Fuel Gauge out the hood.

Do you run an automatic?

PS you can buy a MAF adapter and not have to grind the  down. 

-Z

Herky-Jerky

Reply #13 –
Hmm I run an A9P with an F2VF MAF with no problem (I have an AOD trans). I'm not running an adjustable regulator (still have a stock Motorcraft one) but I do have a 155 lph fuel pump. An afpr really won't help as the EEC just learns to adjust for the increase in fp, so you're right back where you started from. I bet you need 24lb injectors with your combo. I know I do with my combo. I'll be swapping 24s in this spring along with a new MAF.

I know they sell MAF adapters but I have a bench grinder. In less than 10 minutes I went from  to round end MAF ;)
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Herky-Jerky

Reply #14 –
Mine has surged/bucked on deceleration from day one and that was with a std MAF & 19Lb inj or with a 76mm Pro-M MAF & 24Lb inj... It's not as bad on the A9L stick EEC as on the A9P... So far nothing I've tried has totally cured it...